Gas turbine engine



Dec. 11, 1962 M. SWATMAN 3, 81;

GAS TURBINE ENGINE Original Filed June 15, 1959 4 Sheets-Sheet 1 "441VM. SW4 TMAN INVENTOR.

.4 TmRA/EKS 1962 I. M. SWATMAN 3,067,981

GAS TURBINE ENGINE Original Filed June 15, 1959 4 Sheets-Sheet 2 F/G,Z"(4N MSWATMAN INVENTOR.

ATTOPNEKS- Dec. 11, 1962 Original Filed June 15, 1959 I. M. SWATMAN GASTURBINE ENGINE 4 Sheets-Sheet 3 I MN M. SMTMAN INVENTOR.

A 7' TOR NE KS Dec. 11, 1962 I. M. SWATMAN 3,067,931

GAS TURBINE ENGINE Original Filed June 15, 1959 4 Sheets-Sheet 4 F/GiIWN MSMTMA/V 11v VENTOR. m

BYWM I- A TTORNEKS' United States Patent Claims. (Cl. 253-39) Thisinvention relates to a gas turbine engine and more particularly to anovel means for supporting a turbine wheel shroud and scroll assembly ina gas turbine engine.

This application is a divisional application of copending applicationSerial No. 820,323, filed June 15, 1959, for a Gas Turbine Engine.

In the present invention there is provided a gas turbine engine having aturbine wheel including a shaft rotatably supported in a housing. Aturbine nozzle is supported adjacent the turbine wheel so that the gasesof combustion produced in the engine may be directed by the nozzleagainst the blades of the turbine wheel. The nozzle is concentricallypositioned with respect to the turbine wheel shaft preferably through anozzle support member which is positioned against the shaft by means ofa bearing, and through a plurality of radial pins which engage thenozzle support member and the nozzle. A space is provided between theturbine nozzle support member and the turbine nozzle in which a.

plurality of heat shields are positioned. Cooling air is fed to thisspace which absorbs heat from the turbine nozzle and the heat shields toprevent the bearing from overheating due to the heat supplied the nozzlefrom the motive gases of the engine.

A turbine shroud having an inner peripheral dimension greater than theouter peripheral dimension of the turbine nozzle is positioned over theturbine nozzle and is supported thereby in a sliding fit relationship.The turbine shroud extends in an axial direction a sufiicient distanceto surround the turbine wheel in spaced relationship thereto. Such astructure permits radial differential expansion between the turbinenozzle and the turbine shroud without causing appreciable stresses ineither the nozzle or the shroud. It also permits relative axial movementbetween the turbine shroud and the turbine nozzle.

A turbine scroll assembly, comprising a turbine shroud retainer and ascroll for conveying motive gases to the turbine nozzle, is piloted fromthe turbine shroud. The shroud retainer is positioned over one end ofthe shroud and over a portion of the outer periphery of the shroud sothat the portion of the shroud retainer which engages the shroudmaintains a substantially fixed position relative thereto. Both thescroll and the shroud retainer have radially outwardly extending flangeswhich are affixed to each other. These flanges are supported by aradially extending portion of the housing in a sliding fit relationshipso that the scroll can expand and contract in a radial directionrelative to the housing as engine operating conditions change. Thescroll also has an inwardly extending portion including an axiallyextending flange which surrounds a portion of the housing in a slidingfit relationship so that the scroll is free to expand and contract in anaxial direction relative to the housing.

Means are provided to limit the axial movement of the shroud withrespect to the turbine nozzle and this means may comprise a portion ofthe turbine scroll assembly which is capable of engaging both ends ofthe shroud. For example, a portion of the shroud retainer may bepositioned over one end of the shroud,

bearings 17 and 18. The outer races of these bearings '25 and 26.

3,657,981 Patented Dec. 11, 1962 ICC while a portion of the scroll maybe positioned adjacent the other end thereof.

An object of the present invention is the provision of means forcontrolling the spacing between a turbine wheel and a shroud surroundingthe turbine wheel during transient thermal conditions.

Another object of the invention is to provide a shroud for a turbinewheel which is supported by a turbine nozzle in a manner to permitdifferential expansion and contraction of the turbine nozzle in relationto the shroud.

Another object of the invention is to provide means for preventingoverheating of turbine shaft support bearings due to the heat from themotive gases of the engine.

A further object of the invention is the provision of means forpositioning a turbine scroll assembly relative to a turbine wheel andnozzle.

Still another object of the invention is the provision of means in a gasturbine engine for positioning a turbine scroll assembly relative to aturbine wheel and nozzle and for supporting the turbine scroll from thehousing of the engine in such a way as to permit difierential movementof the scroll relative to said housing during transient operatingconditions of the engine.

Other object and attendant advantages of the invention will become moreapparent as the specification is considered in connection with theannexed drawings in which:

FIGURE 1 is a rear elevational view of a gas turbine engine in which thepresent invention may be employed;

FIGURE 2 is a partial cross sectional view of the gas turbine enginetaken along the lines 2-2 of FIGURE 1 with certain portions shown inelevation;

FIGURE 3 is a sectional view taken along the lines 3-3 of FIGURE 2;

FIGURE 4 is a partial sectional view taken along the lines 4-4 of FIGURE1.

Referring now to the drawings in which like reference numerals designatelike parts throughout the several views thereof, the numeral 10designates a first portion of the housing for the gas turbine engine ofthe present invention. This portion of the housing carries a supportstructure 11 in which the output shaft 12 of the engine is rotatablysupported. The first portion of the housing is received in a secondportion 13 and is secured thereto by suitable means such as a pluralityof bolts 14.

Referring specifically to FIGURE 2, a turbine wheel 15 including a shaft16 is rotatably supported in portion 10 of the housing by means of apair of antifriction engage the housing 10 and are retained therein bymeans of a bearing retainer 19 which engages the outer race of bearing18 and positions the outer race of bearing 17 against shoulder 20 of thehousing. The bearing retainer is secured to the housing 10 by means of aplurality of screws, one of which is shown at 21. A

sleeve 22 surrounding the shaft 16 and keyed thereto by means of a key23, is forced against the inner race of the bearing 13 by means of a nut24 threaded onto the shaft 16 which in turn forces the inner race ofbearing 17 against a shoulder on shaft 16. The force of the nut istransmitted to the sleeve by means of washers The turbine wheel 15 andthe shaft 16 are thus rotatably supported in the housing 10 and arepositively positioned axially in the housing 10 by the above describedstructure.

A turbine nozzle support member 27 having an axially extending box 28fitting into a bore 31 in the housing 10 is positioned over the end ofthe housing 10 and is affixed thereto by means of a plurality of screws32.

A sleeve type bearing 33 positioned between the turbine nozzle supportmember 27 and shaft 16, aids the bearings 17 and 18 in rotatablysupporting the turbine wheel and shaft 16 in the housing 10.

A turbine nozzle generally designated by the numeral 34, including aplurality of blades supported from an outer platform 36 and an innerplatform 37 having an inner peripheral dimension or diameter greaterthan the outer peripheral dimension of the main body portion 38 of thenozzle support member 27, is supported from the nozzle support member bya plurality of radial pins 41. These radial pins pass through bores 42in the inner platform 37 of the turbine nozzle, through the annularspace between the inner platform 37 and the main body portion 38 of theturbine nozzle. support member and into bores 43 in the main bodyportion 38 of the turbine nozzle support member 27. The bores 42 in theinner platform of the turbine nozzle and the bores 43 in the main bodyportion 38 of the turbine nozzle support are made slightly larger thanthe diameter of the pins 41 so that the pins engage these two members ina sliding fit relationship. The radial outward movement of the pins islimited by the turbine scroll assembly as shown. The radial pins 41 thusposition the turbine nozzle concentrically with respect to the shaft 16but permit the turbine nozzle 34 to expand and contract radially duringdifferent operating conditions through sliding action on the radialpins.

A plurality of heat shields, preferably three in number, designated bythe numerals 44, 45 and 46, and having different diameters arepositioned in the annular space between the inner platform 37 of thenozzle 34 and main body portion 33 ofthe nozzle support member 27. Theouter dimension of the largest heat shield 44 is less than the innerdimension of the inner platform 37 while the inner dimension of thesmallest heat shield 46 is greater than the outer dimension of the mainbody portion 38 of the turbine nozzle support member 27. Each of theheat shields has a plurality of bores represented by the numeral 47 forreceiving the radial pins 41 which support the heat shields in spacedrelationship with respect to the inner platform 37 of the turbine nozzleand the main body portion 38 of the nozzle support member. The radialpins also support the heat shields in spaced relation to each other. Theheat shields are preferably formed of a material having a highlyreflective outer surface for purposes which will be describedsubsequently. The material employed is preferably stainless steel suchas SAE 30321 or 30347.

A seal retainer 51, having an axially extending flange 52 positioned ina bore 53 in the turbine support member 27, is secured to the turbinesupport member by means of the screws 32 previously mentioned. The sealretainer has an axially extending flange 54 extending toward the turbinewheel 15 for carrying a sleeve 55 which surrounds a labyrinth seal 56aflixed to the shaft 15. The seal retainer 51 extends radially outwardlyto a position approximately co-terminus with the outer periphery of theinner platform 37 of the turbine nozzle and forms an annular spacetogether with a radially extending flange 57 on the turbine nozzlesupport member for receiving heat shields 44, 45 and 46 and the innerplatform 37 of the turbine nozzle.

A cooling air seal 61 is positioned against the seal retainer 51 bymeans of the screws 32. This cooling air seal has a radially inwardlyextending flange 62 which engages the axially extending flange 54 of theseal retainer 51 to properly position the arm 63 of the seal withrespect to the turbine wheel 15.

The tips of the blades 35 of the turbine nozzle 34 preferably lie in animaginary cylinder as is apparent from an inspection of FIGURE 3. Ashroud 64 with a cylindrical portion 65 having an internal diameterslightly larger than the diameter of this imaginary cylinder ispositioned over the tips of the nozzle blades so that the cylindricalportion of the shroud surrounds the tips of the nozzle blades in asliding fit relationship. A portion 66 of the shroud extends axially andradially outwardly from the cylindrical portion 65 in spacedrelationship over the tips of the blades 67 of the turbine wheel. Enoughclearance is provided between the tips of the nozzle blades 35 and thecylindrical portion 65 of the shroud to permit differential radialexpansion between these two members without setting up undue stresses inthe shroud or the nozzle. This prevents warping of the shroud andmaintains the concentricity of the shroud with respect to the tips ofthe turbine wheel blades during all operating conditions of the engine.For example, approximately .001 clearance may be provided between thetips of the nozzle blades 35 and the cylindrical portion 65 of theshroud around the entire circumference thereof for a nozzleapproximately 8 inches in diameter. This clearance also permits relativeaxial movement between the turbine shroud and the nozzle blades.

A turbine scroll assembly is provided for supplying m0- tive fluid-hotcombustion gases from a combustion chamber (not shown)to the turbinenozzle and turbine wheel. This turbine scroll assembly comprises ashroud retainer 71, having a radially outwardly extending flange r 72,and a scroll 73 also having a radially outwardly extending flange 74.The radially outwardly extending flanges '72 and 74 are fastenedtogether by suitable means such as bolt and nut assemblies shown at 75.

The shroud retainer '71 extends in spaced relation over the shroud 64,and has a radially inwardly extending flange 76 which fits over one endof the shroud and limits axifl movement of the shroud in this direction.A small clearance is provided between the end of the shroud and theflange 76 so that stresses will not be set up in the shroud when theengine is operating at high temperatures. The shroud retainer 71 engagesa portion of the outer periphery of the shroud as at 77 in a loose fitrelationship, for example a few thousandths of an inch clearance isprovided when the engine is cold, and this positions or pilots theturbine scroll assembly in the engine since the turbine scroll assemblyis free to move radially or axially at other positions where it comesinto engagement with the housing or other components of the engine aswill presently be explained. The radially extending flange 74 of thescroll is supported by a radially inwardly extending flange 78 of thehousing 13 through the studs 81 and nuts 82. The bores 80 in the housing13 that receive the studs 81 are made considerably larger than thediameter of the studs and the nuts are torqued to a predetermined valueto permit sliding between the faces of the flanges 74 and 78which aremachined to reduce friction. This permits the turbine scroll assemblywhich operates at considerably higher temperatures than the housing togrow radially as the turbine scroll assembly rises in temperature and tocontract radially when the temperatures are lowered.

The scroll 73 also has an axially extending flange 83 which aids insupporting the main portion of the scroll through radially inwardlyextending flange 84. The axially extending flange 83 surrounds a portionof the housing 10 which supports the bearings 17 and 18, the turbinewheel 15 and shaft 16. The flange 83 is supported by the housing througha pair of piston rings 85 and 86 thereby permitting freedom of movementof the scroll assembly at this position and providing a seal to preventleakage of the hot combustion gases. This construction also permitsliberal machining tolerances between the housing and the scroll. Axialexpansion and contraction of the shroud assembly is permitted by reasonof the fact that the main portion of the scroll 73 is made of thin metalthat can deform under stress. Thus during transient thermal conditionsthe flange 83 may slide relative to the housing on piston rings 85 and86 even though the flange member 74 is maintained stationary in an axialdirection with respect to the housing.

It can be seen from an inspection of FIGURE 2 that the turbine nozzlesupport member 27 is positioned axially in the engine and is supportedby the first portion of the housing structure. This locates or positionsthe turbine nozzle 34 and the blades 35 axially in the engine. Theturbine shroud 64 is positioned to be engaged by the radial flange 74 ofthe turbine scroll 73. The sliding fit relationship between the shroud64 and the tips of the nozzle blades 35 permits relative axial movementbetween these two structures. It permits, therefore, axial dimensionalchanges between the first portion 19 of the housing and the secondportion 13 of the housing to which the radial flange 74 is attachedwithout setting up bending stresses in the nozzle 34 and the nozzlesupport member 27 which would occur if the shroud 54 andthe nozzle 34were formed integral. It can be seenthat there may be axial differentialexpansion between the first portion 10 of the housing and the secondportion 13 of the housing during transient temperature conditions. Inthis case, axial movement will take place between the shroud 64 and theturbine nozzle 34, since the radial flange 74 of the scroll 73 ispositioned in engagement with and will move axially with flange 78.

Lubricating oil is conveyed to the housing 10 from a pump (not shown) byway of a conduit 91 which is threaded into the housing at 92. From theconduit 91 lubricating oil is supplied to the bearing 33 via conduits93, 94 and 95, oil transfer tube 96 and groove 97. Lubricating oil issimilarly supplied to the bearings 17 and 18 via conduits 93, 98, 101,1&2 and 103.

A planetary reduction gear train generally designated by the numeral 194and partially shown in FIGURE 2 is employed to reduce the speed of theturbine wheel shaft 16 so that usable speeds, to drive a load, such as amotor vehicle, are available at the output shaft 12. This gearing islubricated with oil flowing through the conduits 93, 105 and 106. Sincethis gear train forms no part of the present invention, and anyconventional gear train may be employed, a further explanation thereofis deemed unnecessary. The lubricating oil used in the lubrication ofthe bearings 17, 18 and 33 and the gear train 1% falls to the bottom ofthe housing 10 and may be scavenged through the bore 107 which may besuitably connected to a lube oil pump through conduits not shown.

. Cooling air for the turbine wheel 15, the turbine nozzle 34 and theheat shields 44, 45 and 45 is supplied to the portion 10 of the housing,through conduit 111 (see FIG- URE 1) from a suitable source (not shown).For example, this air may be bled from the compressor of the engine.Referring now to FIGURE 4, it can be seen that the air supplied from theconduit 111, flows through conduits 112 and 113 in the housing, throughair transfer tube 114 positioned between the housing and the turbinenozzle support member 27, through bores 115 and 116 in the turbinenozzle support member into the space between the inner platform 37 ofthe turbine nozzle and the main body portion 38 of the turbine supportmember. The cooling air leaves this space via a plurality of airtransfer tubes, one of which is shown at 117 in FIG- URE 2. Cooling airunder pressure fills the entire space between the inner platform of theturbine nozzle and the main body portion of the turbine support memberas the cross sectional area of all the air transfer tubes 117 is lessthan the cross sectional area of the inlet bore 116. From this space thecooling air flows through the air transfer tubes 117 into the spacedefined by the turbine wheel and the cooling seal 61 where it ismaintained a-t'a pressure approximately 1 p.s.i. above the gas flowingthrough the nozzle 35 and past the turbine blades 67. From this spacethe cooling air flows out into the gas stream through the restrictedflow path defined between the turbine wheel 15 and the arm 63 of thecooling air seal 61. Cooling air also flows through the labyrinth seal55 into the space between the nozzle support member 27 and the sealretainer 51 thereby preventing any lubricating oil from leaking throughthe labyrinth seal. From this space, the cooling air flows through thebore 118 in the nozzle support member 27 into the housing 10 where itmay be exhausted to atmosphere through a breather in the housing (notshown). By maintaining the pressure of the cooling air in the spacebetween turbine wheel 15 and the cooling seal 61 slightly above that ofthe combustion gases, the gases are prevented from flowing through thelabyrinth seal 56 thus preventing hot combustion gases from reaching thebearings 33, 17 and 13.

As can be appreciated by the above description and by reference to thedrawings, the cooling air not only cools the center of the turbine wheel15 to prevent overheating of the turbine wheel and of the shaft 16, butalso serves to remove heat from the heat shields 44, 4S and 46, theradial pins 41, the turbine nozzle 34 and the turbine nozzle supportmember 27 to prevent the bearing 33 from becoming overheated because ofthe heat from the nozzle 34. As previously pointed out, the heat shieldsare constructed of a material having highly reflective surfaces such asstainless steel. These highly reflective surfaces tend to reflect theheat emanating from the turbine nozzle 34, particularly inner platform37 thereof, and thereby aid in preventing turbine nozzle support member27 and bearing 33 from becoming overheated. The reflection of the heatradiated from the inner platform 37 of the turbine nozzle back againstthe undersurface thereof prevents a large thermal gradient across theinner platform thereby preventing overstressing and cracking.

Thus, the present invention provides a means for supporting a turbineshroud in concentric spaced relationship over the tips of the blades ofa turbine wheel, as well as means for maintaining this concentricityduring transient operating conditions of a gas turbine engine in whichthese means are employerd. In addition, the invention provides means forsupporting a turbine scroll assembly in a gas turbine engine which willpermit difierential expansion and contraction of the scroll assemblywith respect to housing of the engine during transient opera-tingconditions.

It will be understood that the invention is not to be limited to theexact construction shown and described, and that various changes andmodifications may be made Without departing from the spirit and scope ofthe invention, as defined in the appended claims.

What is claimed is:

1. In a gas turbine engine, a housing, a turbine wheel including a shaftrotatably supported in said housing, a turbine nozzle, means forsupporting said turbine nozzle adjacent said turbine wheel, a turbinewheel shroud positioned in a sliding fit relationship over the outerperiphery of said turbine nozzle and extending in spaced relationshipover the periphery of said turbine wheel, said sliding fit relationshipbeing sufficiently great to permit relative axial movement between thenozzle and the shroud during all operating temperatures of the engineand being sufliciently small to maintain the shroud in spacedrelationship over the outer periphery of the turbine wheel during alloperating temperatures of the engine, a turbine scroll assembly pilotedfrom said turbine wheel shroud, said turbine scroll assembly beingsupported by said housing in a sliding fit relationship to permitdifferential expansion and contraction between said turbine scrollassembly and said housing, a portion of said turbine scroll assemblyengaging the ends of said turbine wheel shroud to limit the axialmovement thereof with respect to said turbine nozzle.

2. In a gas turbine engine, a housing, a turbine wheel including a shaftrotatably supported in said housing, a turbine nozzle, means forsupporting said turbine nozzle adjacent said turbine wheel, a turbinewheel shroud supported by said turbine nozzle and extending inspacedrelationship over the periphery of said turbine Wheel, saidhousing having a radially extending portion and an axially extendingportion, a turbine scroll assembly piloted from said turbine wheelshroud, said turbine scroll assembly having a radially extending portionsecured to said radially extending portion of said housing in a slidingfit relationship to permit expansion and contraction of said turbinescroll assembly relative to said housing in a radial direction, saidturbine scroll assembly also having an axially extending portionpositioned in a sliding fit relationship against said axially extendingportion of said housing to permit axial expansion and contraction ofsaid turbine scroll assembly relative to said housing in an axialdirection.

3. In a gas turbine engine, a housing, a turbine wheel including a shaftrotatably supported in said housing, a turbine nozzle, means forsupporting said turbine nozzle adjacent said turbine Wheel, a turbinewheel shroud po-. sitioned in a sliding fit relationship over saidturbine nozzle and supported thereby, said turbine shroud extending inspaced relationship over the periphery of said turbine wheel, the outerperipheral dimension of said turbine nozzle being smaller than the innerperipheral dimension of said shroud by an amount large enough to permitaxial movement between the turbine nozzle and the shroud during alloperating conditions of the engine and by an amount small enough tomaintain the shroud in spaced relationship over the periphery of theturbine wheel during all operating conditions of the engine, saidhousing having a radially extending portion and an axially extendingportion, a turbine scroll assembly piloted from said turbine wheelshroud, said turbine scroll assembly having a radially extending portionsecured to said radially extending portion of said housing in a slidingfit relationship to permit expansion and contraction of said turbinescroll assembly relative to said housing in a radial direction, saidturbine scroll assembly also having an axially extending portionpositioned in a sliding fit relationship against said axially extendingportion of said housing to permit axial expansion and contraction ofsaid turbine scroll assembly relative to said housing in an axialdirection, a portion of said turbine scroll assembly engaging the endsof said turbine wheel shroud to limit the axial movement thereof withrespect to said turbine nozzle.

4. In a gas turbine engine, a housing, a turbine wheel including a shaftrotatably supported in said housing, a turbine nozzle supported adjacentsaid turbine wheel, a turbine wheel shroud supported by said turbinenozzle and extending in spaced relationship over the periphery of theturbine wheel, the outer periphery of said turbine nozzle and the innerperiphery of said shroud being so dimensioned to provide a sliding fitclearance between the nozzle and the shroud, said clearance beingsufficiently great to maintain said sliding fit clearance during alloperating temperatures of the engine and being sufficiently small tomaintain the shroud in spaced relationship over the periphery of thetubine Wheel during all operating conditions of the engine, wherebyrelative axial movement between said turbine wheel shroud and saidturbine nozzle is permitted during all operating temperatures of theengine.

5. In a gas turbine engine, a housing, a turbine wheel including a shaftrotatably supported in said housing, a turbine nozzle supported by saidhousing adjacent said turbine Wheel, a turbine shroud positioned inasliding fit clearance over said turbine nozzle and supported thereby,said turbine shroud extending in spaced relationship over the peripheryof said turbine Wheel, the sliding fit clearance between said turbinenozzle and said turbine shroud being large enough to maintain a slidingfit relationship between said turbine shroud and said turbine nozzleduring all operating temperatures of the engine, and small enough tomaintain the shroud in spaced relationship over the periphery of theturbine wheel during all operating temperatures of the engine, a turbinescroll assembly piloted from said turbine shroud and having meansengaging the ends of said turbine shroud, said turbine scroll assemblyengaging said housing in a sliding fit relationship.

References Cited in the file of this patent UNITED STATES PATENTS2,427,244 Warner Sept. 9, 1947 2,429,990 Burgess Nov. 4, 1947 2,488,875Morley Nov. 22, 1949 2,494,328 Bloomberg Jan. 10, 1950 2,654,566 Boyd etal. Oct. 6, 1953 2,925,245 Lusch Feb. 16, 1960 2,925,998 Hayes Feb. 23,1960 FOREIGN PATENTS 345,888 Great Britain Apr. 2, 1931 705,381 GreatBritain Mar. 10, 1954

